Electron doping in the ferromagnetic and metallic double perovskites ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ is achieved via the partial substitution of ${\mathrm{Sr}}^{2+}$ by ${\mathrm{La}}^{3+}.$ We show that this doping promotes an extraordinary rising of the Curie temperature of about 70 K above that of the pristine compound. This finding reveals that the ferromagnetic coupling is mediated by itinerant carriers, thus providing solid experimental support to the double-exchange picture for the magnetic interactions. The observation that $T_C$ can be substantially enhanced may be of relevance for technological applications of these materials in advanced spin devices.

• Received 30 January 2001

DOI:https://doi.org/10.1103/PhysRevB.64.092411